Conventionally, draft gears employ a combination of springs and friction elements to absorb shocks that occur as a result of pulling and buffing forces applied to the railroad car coupler and reduce the magnitude of those shocks as applied to the car frame, body and content. Conventional draft gears of this type position the spring within the draft gear body, with the friction elements being positioned adjacent the open end of that body. These friction elements act between the inner wall of the body at the open end to provide a frictional force absorption related to the magnitude of the applied force.
In the present invention a plunger is telescoped into the draft gear body, the spring elements are placed within the plunger and the friction elements are deep within the body cavity (as compared to the prior art practices) to act on the inside of the walls of the plunger. A number of advantages over the prior art practices which incorporate spring and friction elements are thereby achieved, which advantages include: Since the plunger telescopes within the body it is guided by the body both at the open end of the body and deep within the body cavity. This provides stabilization and reduces the tendency of the plunger to cock, i.e., becomes misaligned, with respect to the body. The shock absorbing elements are deep within the body cavity and are thus protected against deleterious action which can occur when those elements are exposed. The construction permits friction to be developed not only between the shoes acting on the inner walls of the plunger as a result of the action of the fixed wedges, but also between the outer walls of the plunger and the inner walls of the body. This enhances the possibility for a shorter draft gear since the amount of force reaction required to be provided by the spring element can be reduced. The possibility of shortening the draft gear also is enhanced in that in some embodiments the friction elements can surround the spring elements, rather than in a linear series as is the case with prior art practices. The friction elements may also be cascaded to obtain a multiplication of the force-absorption which the friction elements provide. Embodiments may be made using tubing rather than castings to thereby achieve manufacturing cost reduction of comparable strength units.
In such embodiments the body length is not a limiting factor to the spring length as is the case in prior art devices. Using the present invention, draft gears can be provided which having a long travel (extent of movement upon impact).
Further objects and advantages will become apparent from the following description and attached drawings.